THE EFFECT OF THERMAL AGING ON THE ABRASIVE WEAR BEHAVIOR OF AGE-HARDENING 2014-A1 SIC AND 6061-A1/SIC COMPOSITES/

This paper examines changes to the abrasive wear resistance of alumini um-based composites when heat-treated to different ageing conditions. The composites studied were the age-hardenable aluminium alloys 2014 A l or 6061 Al reinforced with 3 mu m or 20 mu m SiC particles. The mate rials were aged at temperatures between 50 degrees C and 250 degrees C , and changes to the wear resistance were measured using a pin-on-drum machine. When aged at the lowest temperatures (between similar to 50- 150 degrees C), transmission electron microscopy revealed the presence of the solute clusters (e.g. GP zones) and small coherent precipitate s in the aluminium alloy matrices, and these were easily sheared by mo bile dislocations. Consequently, the hardness and abrasive wear resist ance of these under-aged composites were measured to be relatively low . Raising the ageing temperature to similar to 200 degrees C increased the hardness and abrasion resistance of the composites to the peak-ag ed condition, and this was associated with the precipitation of small intermetallic compounds which were incoherent with the crystal structu res of the aluminium alloy matrices. At 250 degrees C the composites w ere over-aged, and this resulted in a reduction in hardness and wear r esistance due to the coarsening of the intermetallic precipitates. The composites containing 20 mu m SiC particles were slightly more wear r esistant than those containing 3 mu m SiC.